In recent years, as the performance of an information processor such as a computer is increasing, using optical transmission also for communication between chips on boards in an information processor or between boards has been proposed.
Such an optical transmission technique is also referred to as optical interconnection, which is an optical communication technique of transmitting a light signal in a relatively short distance such as between devices, between boards, between chips, or the like. The speed in the optical interconnection is higher than the speed in a conventional metal wire. By using the optical interconnection, improvements in characteristics such as power consumption of a device, EMI, noise, loss, and the like are expected.
In order to simultaneously transmit a plurality of light signals in an optical interconnection, arranging semiconductor lasers has been considered.
However, when a plurality of semiconductor lasers are disposed so as to be integrated at high density, there is a possibility that temperatures of the semiconductor lasers vary due to heat generation of the semiconductor lasers. The oscillation wavelength of the semiconductor laser changes according to the temperature of a gain region which oscillates a laser beam. There is consequently a case that the oscillation characteristic of each semiconductor laser is influenced by the variations in the temperature.    Japanese Laid-open Patent Publication No. 7-211934    Japanese Laid-open Patent Publication No. 6-53607    Japanese Laid-open Patent Publication No. 2003-209313